This invention relates to tools and apparatus for cutting into existing lines carrying fluids such as gas or water under pressure for the purpose of adding additional lines to carry such fluids.
In a typical fluid transport system, such as the system supplying water to an average neighborhood, a main water line is buried underground. Branch lines draw water from this main line and deliver water to homes through out the neighborhood. When a new home or other facility is constructed in the neighborhood, it is necessary to connect (or xe2x80x9ctapxe2x80x9d) the new branch line into the main line. It is imperative that the connection be made without disrupting water service to the other existing homes in the neighborhood. Such a connection under pressure is called a xe2x80x9chot tapxe2x80x9d or xe2x80x9clive tapxe2x80x9d.
There are various techniques and instruments that may be used to accomplish the hot tapping of a main line. One example may be found in U.S. Pat. No. 4,902,174 that issued on Feb. 20, 1990 and is assigned to Cliffside Utility Contractors Ltd. As described in the patent, the first step is to secure a xe2x80x9csaddlexe2x80x9d to the pipe. The saddle is a device that surrounds the pipe and provides a recessed area containing a seal which is flat or otherwise matches the curvature of the pipe. The saddle typically has a threaded collar projecting away from the pipe at the location of the seal, as well as an opening such that a cutting device can pass through the collar to cut into the pipe. A valve device is mounted to the saddle and the hot tapping device mounted to the valve device. Once the cut has been made into the pipe, the hot tapping device is withdrawn and the valve is closed. The device then can be removed, the branch line attached to the valve device, and the valve opened placing the branch line in fluid communication with the main line.
One problem associated with the prior art is the buildup of fluid which has xe2x80x9cleakedxe2x80x9d into the interior of the tool during the cutting operation. Additionally, it has been noted that the cutting operation often leaves undesired residue within the main pipe itself. It is therefore a paramount object of the present invention to provide for a hot tapping tool that is easy to operate and has few moving parts, minimizes and prevents escaping of fluids from the line being cut during the cutting operations, and to minimize or other wise reduce problems caused by cutting debris that is frequently left following a cutting operation in the pipe line itself. This and other objects of the present invention that will become apparent upon a reading of the detailed description with the appended drawings are addressed by the present invention as described below.
The present invention involves an improvement to a hot tapping tool adapted to be secured to and cutting into a pipe line carrying a fluid under pressure. The tool generally includes a housing, a shaft supported at spaced locations for rotation and axial movement within the housing, and a cutting device secured to one end of the shaft for cutting into the pressurized pipe line. The tool has a first fluid sealing member sealing an upper end of the housing against external leakage of fluid entering the tool during the cutting operation of the pressurized pipe and a second fluid sealing member sealing a lower end of the housing to minimize entrance of fluid into the tool during cutting of the pressurized pipe line. The tool is further provided with a pressure relief valve for allowing fluid under pressure within the housing to be released to the atmosphere. Still another important aspect of the present invention involves element for retaining a portion of the pressurized pipe cut from the pipe line by the device upon retraction of the device from the pipe line.